I just looked at fares for Paris, Rome and Geneva on the same dates. The fares to Paris were about $500 cheaper than the flights to Rome.
Is this normal? Are flights to Paris usually cheaper than flights to Rome or was it just the date?

Is there any city in Europe that is consistently cheaper than the others?

DH and I are looking into a holiday in Europe and we're not really fussy about which city we land in other than not London because we need to hire a car and driving an English car on the continent is a PITA.